This invention relates generally to the testing of electronic modules, and more particularly to a test system, a test contactor and a test method for testing electronic modules.
Electronic modules, such as semiconductor memory modules, multi chip modules, semiconductor carriers, semiconductor packages, and microprocessors are routinely tested during manufacture. The modules include terminal contacts in electrical communication with the electronic devices contained on the modules. For performing various test procedures on the modules, temporary electrical connections are made to the terminal contacts.
One type of prior art electronic module 10, which is illustrated in FIGS. 1A and 1B, includes a substrate 12, and multiple semiconductor packages 16 mounted to the substrate 12. The module 10 also includes a row of terminal contacts 14 on the substrate 12 in electrical communication with the integrated circuits contained on the semiconductor packages 16. The terminal contacts 14 comprise generally planar, in-line metal pads located on opposing sides of the substrate 12 along a lateral edge 18 thereof. The substrate 12 typically comprises an electrically insulating material such as a glass filled plastic (FR-4), or a ceramic. In addition, the substrate 12 includes through openings 19 which facilitate indexing and handling by automated test equipment and carriers.
For testing the electronic module 10 test systems have been developed and are commercially available from various manufacturers. These test systems are configured to make temporary electrical connections with the terminal contacts 14. In addition, the test systems are configured to apply test signals through the terminal contacts 14 to the electronic devices on the module 10, and then to analyze the response signals from the electronic devices. Often times these test systems merely test the gross functionality of the module 10, as the semiconductor packages 16 on the module 10 have been previously individually tested and burned-in.
The test systems typically include test boards and test circuitry in electrical communication with the test boards. In addition, the test boards typically include interface boards having test contactors configured to physically and electrically engage the terminal contacts 14 on either side of the module 10. In general there are two types of test systems, which are sometimes referred to as xe2x80x9cpass through test systemsxe2x80x9d, or xe2x80x9csocket test systemsxe2x80x9d.
FIG. 1C illustrates a pass through test system 11PT having an interface board 13PT, and test contactors 15PT on the interface board 13PT. The test contactors 15PT are in electrical communication with test circuitry (not shown). In addition, the test contactors 15PT are movable from an inactive (open) position in which the terminal contacts 14 on the module 10 are not engaged, to an active (closed) position in which the terminal contacts 14 on the module 10 are physically and electrically engaged.
As shown in Figure 1C, with the test contactors 15PT in an inactive (open) position, the module 10 can be indexed into a contactor area between the test contactors 15PT, as indicated by arrow 17PT. With the module 10 located in the contactor area, the test contactors 15PT can be mechanically moved to the active (closed) position to physically and electrically engage the terminal contacts 14. The pass through test contactors 15PT are sometimes referred to as being xe2x80x9czero insertion forcexe2x80x9d (ZIF) contactors because temporary electrical connections can be made without an insertion force being placed on the module 10.
FIG. 1D illustrates a socket test system 11S having an interface board 13S, and test contactors 15S on the interface board 13S. In this case, the test contactors 15S are normally in an active (closed) position, but are mechanically moved to an inactive (open) position as the module 10 is inserted from above as indicated by arrow 17S. When the module 10 is in place, the test contactors 15S move back to the active (closed) position to physically and electrically engage the terminal contacts 10. The socket test contactors 15S are sometimes referred to as being xe2x80x9clow insertion forcexe2x80x9d (LIF) contactors because an insertion force is exerted on the module 10 in making the temporary electrical connections with the test contactors 15S.
One advantage of the pass through test system 11PT (FIG. 1C) over the socket test system 11S, is that no insertion forces are exerted on the module 10 to provide electrical engagement for testing. Accordingly, less physical stress is placed on the module 10 during testing with the pass through test system 11PT. Also, as the number of terminal contacts 14 on the module 10 increases, the insertion forces exerted by the socket test system 11S increase. The socket test system 11S can therefore damage the module 10, or the terminal contacts 14 on the module 10, and can be more expensive to operate and maintain.
The present invention is directed to an improved pass through test system. In pass through test systems it is desirable to make temporary electrical connections with the terminal contacts 14 on the modules 10 that are reliable, and have low electrical resistance. This requires that the terminal contacts 14 be scrubbed, or alternately penetrated by the test contactors 15PT, such that oxide layers and surface contaminants on the terminal contacts 14 do not adversely affect the temporary electrical connections. However, in scrubbing or penetrating the terminal contacts 14, damage to the terminal contacts 14 and modules 10 must be minimized.
It is also advantageous in pass through test systems for the temporary electrical connections to provide electrical paths that are short in length to facilitate the application of high speed test signals, and to prevent capacitive coupling and the introduction of noise and spurious signals. Further, it is advantageous to make, and then break, the temporary electrical connections as quickly as possible, to facilitate a high throughput for the test procedure.
The pass through test system of the invention includes test contactors configured to make temporary electrical connections that are reliable, have low electrical resistance, and minimally damage terminal contacts on the modules. In addition, the test contactors are relatively inexpensive to make, provide a high throughput, and can be operated in a production environment with minimal maintenance. Further, the test contactors are designed to electrically engage the terminal contacts with a zero insertion force on the module, and to exert a force for retaining the module on the interface board.
In accordance with the present invention, a pass through test system, a pass through test contactor, and a pass through test method for testing electronic modules are provided. In illustrative embodiments, the test system is configured for testing electronic modules having planar, in-line terminal contacts substantially as previously described.
The test system includes test circuitry configured to generate test signals, and an interface board having contact pads in electrical communication with the test circuitry. The interface board can be mounted to a test board of an automated or manual test handler configured to transport, align, and hold the module on edge on the interface board. The test system also includes test contactors on the interface board configured to physically and electrically engage the terminal contacts on the module, and to simultaneously physically and electrically engage the contact pads on the interface board.
In a first embodiment the test contactors include a base rotatably (pivotably) mounted to the interface board, and cantilevered spring contacts on the base configured to simultaneously scrub and penetrate the terminal contacts on the module, and also the contact pads on the interface board. The base and the spring contacts are rotatable from a first position (open) in which the terminal contacts are not engaged, to a second position (closed) in which the terminal contacts are physically and electrically engaged. Also, the base comprises molded plastic, and the spring contacts comprise resilient metal leaf springs embedded in the plastic. The spring contacts include leaf spring end portions for electrically engaging the terminal contacts on the modules, and leaf spring middle portions for electrically engaging the contact pads on the interface board.
In a second embodiment the test system includes an interface board and slidably mounted test contactors on the interface board. In this embodiment the test contactors include a base configured for sliding movement on the interface board, and short beam contacts on the base for simultaneously electrically engaging the terminal contacts on the module and the contact pads on the interface board. Also, the short beam contacts are oriented at an angle with respect to the surface of the contact pads and terminal contacts, such that forces are generated for making and maintaining the temporary electrical connections.
In a third embodiment the test system includes an interface board, and test contactors mounted on a base slidably mounted to the interface board. The base includes coiled spring contacts configured to generate spring forces for penetrating the terminal contacts. The test system also includes a flex circuit in electrical communication with the spring contacts and the test circuitry, configured to allow free sliding movement of the base on the interface board.
In each of the embodiments, the test contactors are designed to electrically engage the terminal contacts with a zero insertion force (ZIF) on the module. Movement of the test contactors into the terminal contacts can be provided by cams, hydraulic cylinders, motors or any suitable mechanical actuator. In addition, the test contactors are designed to penetrate, or to scrub, the terminal contacts during electrical engagement, and also to help retain the module on the interface board. Further, the test contactors are designed for quick engagement and disengagement with the terminal contacts, and are designed to provide a relatively short electrical path to the terminal contacts.
The test method includes the steps of: providing an interface board comprising a plurality of contact pads in electrical communication with test circuitry; providing a plurality of movable test contactors on the interface board comprising a plurality of spring contacts configured to electrically engage the terminal contacts and the contact pads with a zero insertion force; placing the module on the interface board with the terminal contacts proximate to and aligned with the test contactors; moving the test contactors to physically and electrically engage the terminal contacts and the contact pads with the spring contacts; and applying test signals through the test contactors and the terminal contacts to the module.